The present invention relates to a bone adjuster for increasing or decreasing a space between two opposed bone fragments.
The treatment of inherent deformities or other bone abnormalities using bone lengthening techniques has become more common. For example, such a bone lengthening technique may be employed to mechanically expand a space between bone fragments to allow new bone to grow from the opposed ends of the bone fragments, thereby lengthening or correcting another deformity in the bone.
Various instruments have been developed to facilitate bone lengthening techniques, such as those disclosed, for example, in Japanese Patent Application Laid-Open Publication No. Hei 10-43203.
FIG. 12 shows one conventional bone lengthening instrument. When this conventional bone lengthening instrument is used for distraction of bone fragments, plates 10 and 12 are fastened to the opposed bone fragments and a shaft 14 is screwed through the plate 10 so to have its leading end engaged with the plate 12. This shaft 14 is operated to widen the space between the plates 10 and 12. This increased space between the bone fragments promotes osteogenesis.
This conventional bone lengthening instrument can enlarge the space between the opposed bone fragments, but the direction of enlargement is strictly linear. Therefore, the bone lengthening is limited to filling a linearly enlarged space between bone fragments.
Bone deformities are sometimes caused on a part of skeletal frame having curved portions such as skull, jaw, and face areas, most particularly cheekbones and the skull. When conventional bone lengthening instruments are used to adjust the bone of such a swelled skeletal frame, the bone is formed linearly as described above. It is difficult, or impossible, to form the bone so to have a natural shape along a peripheral skeletal frame having a bulbous portion.
The present invention was achieved in view of the circumstances described above. It is an object of the invention to provide a bone adjuster capable of adjusting any bones in conformity with their shape, including swelled skeletal frame and a linear skeletal frame bones.
To achieve the above object, the present invention is directed to a bone adjuster comprising a first lift plate to be fastened to one of two opposed bone fragments, a second lift plate to be fastened to the other fragment, and an adjusting shaft which is screwed through the first lift plate and has its leading end engaged with the second lift plate. The adjusting shaft is rotated to adjust a distance between the lift plates so as to adjust a space between the opposed bone fragments. The first lift plate is provided with a first mounting plate to be fastened to one of the bone fragments and a screw-in connecting portion which is connected to the first mounting plate and in which the adjusting shaft is screwed; the second lift plate is provided with a second mounting plate to be fastened to the other bone fragment and a catching portion which is connected to the second mounting plate and holds the leading end of the adjusting shaft; and at least the catching portion is connected to the second mounting plate via a hinge.
In a device of the above configuration, the adjusting shaft is extended between the screw-in connecting portion of the first lift plate and the catching portion of the second lift plate and rotated to increase or decrease the space between both the plates so to adjust the space between the bone fragments. The bone adjuster of the invention can linearly adjust the space between the bone fragments and can also adjust a bone in conformity with its skeletal frame, even when the bone fragment to be adjusted has a curved or bulbous portion, because at least the catching portion is pivotally connected to the second mounting plate for supporting it via the hinge.
Specifically, when this bone adjuster is used to adjust a skeletal frame having a bulbous portion, the catching portion is pivoted via the hinge and supported by the second mounting plate at an angle corresponding to the skeletal frame, so that the space between the bone fragments can be expanded to rise up along the peripheral skeletal frame or decreased to become low.
The invention may be configured so that both the screw-in connecting portion and the catching portion of the aforesaid invention pivotably connected to the first mounting plate and the second mounting plate via a hinge respectively.
As described above, both the screw-in connecting portion and the catching portion are connected to the first mounting plate and the second mounting plate via the hinge respectively, so that bone fragments of a largely bulbous bone, such as a skull, can also be adjusted appropriately. Specifically, the screw-in connecting portion and the catching portion are respectively pivoted via the hinge and supported by the mounting plate at an angle corresponding to the skeletal frame, so that, even when a skeletal frame had a sharp degree of curvature, the space between the bone fragments can be expanded to largely rise or be decreased to become low in conformity with its shape.
The bone adjuster of the present invention may also be configure to have a stopping flange formed on the end portion of the adjusting shaft of the aforesaid invention so as to externally protrude from its outer periphery, wherein the catching portion comprises a catching plate having a catching surface to engage with the stopping flange and the catching plate is formed a holding hole in which the end of the adjusting shaft is inserted and held.
By forming the holding hole in the catching plate and the stopping flange on the adjusting shaft, a single type of bone adjuster can be used to increase and to decrease the space between the bone fragments. For example, when the space between the bone fragments is to be expanded, the stopping flange is engaged with the inside catching surface on the opposed side of the screw-in connecting portion of the catching plate, and the adjusting shaft is rotated in this state to enable expansion of the catching plate. On the other hand, to pull the catching plate, the stopping flange is engaged with the outside catching surface of the catching plate, and the adjusting shaft is rotated in this state to.